arXiv subjects

M. Senniappan

Publications and source records attributed to M. Senniappan.

4 recordsLinked to original sources

arXiv2025

Fifteen years of Gamma-Ray Burst observations at Very High Energies with H.E.S.S

We present results from the High Energy Stereoscopic System (H.E.S.S.) follow-up observations of Gamma-ray Bursts (GRBs) between 2004 and 2019. We are focusing on non-detections and providing the most extensive set of very-high-energy (VHE, >100 GeV) upper limits to date. We use this catalogue to constrain the properties of VHE-detected GRBs and compare them to those detected at VHE. Our study finds that VHE-detected GRBs are not a distinct population but are instead associated with bright X-ray afterglows and low redshifts. In addition, we model the multi-wavelength emission of a few of the observed GRBs and discuss the results in the context of their obtained microphysical parameters. The results from this work help put current VHE observations into perspective and highlight the capabilities of next-generation instruments, in detecting fainter and more distant GRBs at VHE.

astro-ph.HE↗

arXiv2023

Sensitivity to point-like sources of the ALTO atmospheric particle detector array, designed for $\rm 200\,GeV$--$\rm 50\,TeV$ $γ$-ray astronomy

In the context of atmospheric shower arrays designed for $γ$-ray astronomy and in the context of the ALTO project, we present: a study of the impact of heavier nuclei in the cosmic-ray background on the estimated $γ$-ray detection performance on the basis of dedicated Monte Carlo simulations, a method to calculate the sensitivity to a point-like source, and finally the required observation times to reach a firm detection on a list of known point-like sources.

astro-ph.IM↗

arXiv2021

Expected performance of the ALTO particle detector array designed for 200 GeV - 50 TeV gamma-ray astronomy

The CoMET is an R$\&$D project aiming to design a very-high-energy (VHE) gamma-ray observatory sensitive to energies above $\sim$ 200 GeV. The science goals include continuous observation of soft-spectrum VHE gamma-ray sources such as Active Galactic Nuclei (AGNs) and transients like Gamma-Ray Bursts (GRBs). With these objectives, CoMET is designed to have a low energy threshold with a wide field-of-view of about 2 sr, at a high altitude, and combines ALTO particle detectors with CLiC air-Cherenkov detectors. In this contribution, we focus on the ALTO particle detector array performance only. Water Cherenkov detectors are used for the detection of secondary particles in atmospheric air showers while scintillators serve as muon counters. A detailed study is presented through air-shower, detector and trigger simulations, followed by the reconstruction of the event parameters and the extraction of the signal (gamma-rays) from the background (cosmic-rays). We present the sensitivity of the ALTO detectors to a list of astrophysical sources using two SEMLA analysis configurations.

astro-ph.IM↗

arXiv2021

Signal extraction in atmospheric shower arrays designed for $\rm 200\,GeV-50\,TeV$ $γ$-ray astronomy

We present the SEMLA (Signal Extraction using Machine Learning for ALTO) analysis method, developed for the detection of $\rm E>200\,GeV$ $γ$ rays in the context of the ALTO wide-field-of-view atmospheric shower array R&D project. The scientific focus of ALTO is extragalactic $γ$-ray astronomy, so primarily the detection of soft-spectrum $γ$-ray sources such as Active Galactic Nuclei and Gamma Ray Bursts. The current phase of the ALTO R&D project is the optimization of sensitivity for such sources and includes a number of ideas which are tested and evaluated through the analysis of dedicated Monte Carlo simulations and hardware testing. In this context, it is important to clarify how data are analysed and how results are being obtained. SEMLA takes advantage of machine learning and comprises four stages: initial event cleaning (stage A), filtering out of poorly reconstructed $γ$-ray events (stage B), followed by $γ$-ray signal extraction from proton background events (stage C) and finally reconstructing the energy of the events (stage D). The performance achieved through SEMLA is evaluated in terms of the angular, shower core position, and energy resolution, together with the effective detection area, and background suppression. Our methodology can be easily generalized to any experiment, provided that the signal extraction variables for the specific analysis project are considered.

astro-ph.IM↗